Exam 2: Lipids Flashcards
General structure of triglycerides
glycerol + 3 fatty acids
-what makes them diff are variations & combos of fatty acids & where it they are on the glycerol backbone
What’s the prodominant type of fat we find in food?
triglycerides
what are the functions of fats in food products?
color, flavor, texture, tenderness, emulsification, cooking medium
Melting points & melting ranges w/ respect to chain length, degree of saturation & types of double bonds
length of fatty acid & degree of saturation affects the melting point LENGTH OF THE ACID (# of CARBONS): -longer = higher the melting point -shorter = lower melting point AMOUNT OF DOUBLE BONDS: -trans has a higher melting point DEGREE OF SATURATION: -# of double bonds inc = MP dec -# of double bonds dec = MP inc (polyunsat = liq at room temp)
(length of chain, type of double bonds, degree of saturation)
what does saturation mean?
product/solution has all the H they can hold
they’re more solid at room temp
less saturated = less solid…
-unsat = oils
What are the diff lipid chemical reactions? (3)
- hydrogenation
- polymerization
- winterizing
Hydrogenation
Force H bonds in polysat in presence of a metal catalyst like nickel (cost effective)
- eliminate double bonds
- increases sat
- increases the solidity of the fat
- beneficial in food product
- detrimental to health bc makes the fat into trans fat
hydrolytic rancidity
Enzymatic rancidity:
BUTTER: where the lipases attack the butter fat & separates into butyric acid.
-salt in fat inhibits the lipase
oxidative rancidity
3 stages:
1. INITIATION: formation of free radicals (free radicals attack carbon) catalyzed by metals (Fe & Cu), light, & heat
2. PROPAGATION: formation of peroxide free radicals & hydroperoxide
propagation continues the formation of free radicals
-This does not end until something happens.
3. TERMINATION: oxidative reaction terminated by reaction of free radicals/peroxides w/ compounds
chem-free radical reaction, involving uptake of O2 & prod of off-odors / flavors
what are ways that lipids can go bad? (2)
Oxidative rancidity & Hydrolytic rancidity
How to prevent/reduce oxidative rancidity?
- can terminate this reaction by ANTIOXIDANTS (bc they use the oxygen & make O2 less avail for rancidity)
- BHT BHA TBHQ (recognize that these are strong antiox: don’t remmeber they’re real names)
- vita c is a nat antiox & citric acid - REFRIGERATION
- PACKAGING
- foil lined; opaque
- remove/force out O2 during packaging - STORAGE
- storing in cool, dry places - OUT OF THE SUN
- METALS: SEQUESTRANTS: citric & ascorbic acid. EDTA to neutralize metals
(1)packing (2) antioxidant (3) metals: sequestrins: citric &
polymerization
free fatty acids join together & make dimers & trimers
- they inc the visocosity
- dec smoke point
- inc over time as the oil continues to be heated
- visible: color may become darker & the grim on the walls as well as on the deep fat fryer
Change its behaviors: what can we do to the oils to change their melting point
Winterizing
intersterification
chilling of oils to remove high MP triglycerols that make oils solid at room temp
-salad dressing companies
—
winterizing & intersterification are almost the same
intersterification: done to change types of FA on the trigly
-relocation & combination
Solid Fat Index
relates to the plasticty of the fat; how hard it is
it varies amoung fat bc some are more solid, etc.
highest solid fat index: cocoa butter: very high solid fat index
the reason why there’s a solid fat index: bc we can have diff triglycerols
How does solid fat index relate to texture?
TENDERNESS: oil: makes more tender
lower the fat solid index: the more tender (# of chews)
higher FSI: flaky
lower SFI:
